KIA Niro: Piston, rings

  1. Clean piston.

(1) Using a gasket scraper, remove the carbon from the piston top.

(2) Using a groove cleaning tool or broken ring, clean the piston ring grooves.

(3) Using solvent and a brush, thoroughly clean the piston.

Warning

Do not use a wire brush.

  1. Check the piston-to-cylinder clearance by calculating the difference between the cylinder bore inner diameter and the piston outer diameter.

Piston-to-cylinder clearance : 0.025 - 0.045 mm (0.0010 - 0.0018 in.)

(1) Using a cylinder bore gauge, measure the cylinder bore diameter at position in the thrust and axial direction.

Cylinder bore diameter : 72.00 - 72.03 mm (2.8346 - 2.8358 in.)

Warning

Warning

Measure at 5mm (0.1969 in.) / 71.5mm (2.8150 in.) / 132.5mm (5.2165 in.) from the top of the cylinder block.

(2) Measure the piston outside diameter at 30 mm (1.1811 in) from top land of the piston.

Piston outside diameter : 71.965 - 71.995 mm (2.8333 - 2.8344 in.)

  1. Select the piston matching with cylinder bore class.

Piston-to-cylinder clearance : 0.025 - 0.045 mm (0.0010 - 0.0018 in.)

(1) Check the cylinder bore size code on the cylinder block side surface.

Cylinder Bore Inner Diameter

Cylinder Bore Inner Diameter

(2) Check the piston size mark on the piston top face.

(2) Check the piston size mark on the piston top face.

Piston Outer Diameter

Piston Outer Diameter

Piston Rings

Piston Rings

  1. Inspect the piston ring side clearance.

     

    Using a feeler gauge, measure the clearance between new piston ring and the wall of ring groove.

    If the clearance is greater than maximum, replace the piston.

Piston ring side clearance : (Standard)
No.1 ring :
0.05 - 0.08 mm (0.0020 - 0.0031 in.) No.2 ring :
0.04 - 0.08 mm (0.0016 - 0.0031 in.) Oil ring :
0.050 - 0.125 mm (0.0020 - 0.0049 in.)

If the clearance is greater than maximum, replace the piston.

If the clearance is greater than maximum, replace the piston.

  1. Inspect piston ring end gap.

To measure the piston ring end gap, insert a piston ring into the cylinder bore. Position the ring at right angles to the cylinder wall by gently pressing it down with a piston. Measure the gap with a feeler gauge.

If the gap exceeds the service limit, replace the piston rings. If the gap is too large, recheck the cylinder bore inner diameter. If the bore is over the service limit, the cylinder block must be replaced.

Piston ring end gap :

(Standard)
No.1 ring: 0.13 - 0.18 mm (0.0051 - 0.0071 in.) No.2 ring: 0.25 - 0.40 mm (0.0098 - 0.0157 in.) Oil ring : 0.10 - 0.40 mm (0.0039 - 0.0157 in.)

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